Aryl substituted 5-methyl-N-(aryl)-1,2,4-triazolo [1,5-a]pyrimidine-2-sulfonamides (I), ##STR1## such as those described in U.S. Pat. No. 4,755,212, are valuable herbicides for the selective control of weeds in agronomic crops. U.S. Pat. No. 4,734,123 recommends as the final step in the preparation of these compounds the cyclization of N-(3-(((aryl)amino)sulfonyl)-1H-1,2,4-triazol-5-yl)amines (II) with appropriately substituted 1,3-dicarbonyl compounds or their synthetic equivalents, for example: ##STR2## Accordingly the cyclizations may be conducted under acidic, neutral or basic conditions in a variety of solvents including, for example, acetic acid, ethanol, butanol, dimethylformamide, dimethylsulfoxide or tetrahydrofuran. Among the difficulties encountered with such cyclizations are depressed yields associated with decomposition of both product and starting material and with formation of undesired isomers, e.g., the 7-methyl isomer. ##STR3##
The discovery of a high yield process with a high selectivity to the desired 5-methyl isomer would be of great interest. Furthermore, the replacement of flammable and toxic organic solvents with environmentally benign water would be of considerable benefit.